1. Field of the Invention
The present invention relates to a non-volatile memory, and in particular, to a resistive non-volatile memory.
2. Description of the Related Art
Flash memory technology is currently the most dominant non-volatile memory technology around, but faces challenges due to disadvantages, such as requirement for high operation voltages, slow operation speeds and poor data retention. Thus, future development thereof has been hindered. Moreover, with the device scaling technology trend, the tunneling effect of ultra-thin gate oxide layers of flash memories has resulted in poor data retention performances of flash memories.
Thus, many new non-volatile memories comprising magnetoresistive random access memories (MRAM), ovonic unified memories (OUM) and resistive non-volatile memories (such as resistive random-access memories, RRAM) have been developed in an attempt to replace flash memories. Among them, resistive non-volatile memories are provided with low power consumption, low operating voltage, high write and erase speeds, long endurance, long retention time, nondestructive reading, multiple memory states, simple fabrication processes, and small sizes. Baek et al. [I. G. Baek et al., in Tech. Dig. of IEDM (2005)] provides a plug bottom electrode to decrease the resistance variation between two stable states. Kim et al. [D. C. Kim et al., Appl. Phys. Lett., 88, 232106 (2006)] provides an IrO2 buffer layer to improve the resistance variation between two stable states, thereby eliminating the problem of memory write failure.
The conventional resistive non-volatile memories suffer an unstable resistive switching problem, and consequently their applications for a non-volatile memory are restricted. Meanwhile, there are two structures for non-volatile memories. One structure is constructed by one transistor and one resistor (1T1R), and the other structure is constructed by one diode and one resistor (1D1R). The 1D1R resistive non-volatile memory has advantages of extreme device scaling, but it has to be associated with a resistor having unipolar resistive switching behavior to achieve 1D1R resistive non-volatile memory functions.
Thus, a non-volatile memory operating under the unipolar resistive switching condition with advantages of long endurance, long retention time, simple fabrication processes and low cost is desired.